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f1a0a376ca
linux/kernel
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Valentin Schneider f1a0a376ca sched/core: Initialize the idle task with preemption disabled 
As pointed out by commit

  de9b8f5dcb ("sched: Fix crash trying to dequeue/enqueue the idle thread")

init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.

As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().

Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().

Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().

Secondary startups were patched via coccinelle:

  @begone@
  @@

  -preempt_disable();
  ...
  cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
2021-05-12 13:01:45 +02:00
..
bpf bpf: Fix leakage of uninitialized bpf stack under speculation 2021-05-03 11:56:23 +02:00
cgroup cgroup: rstat: punt root-level optimization to individual controllers 2021-04-30 11:20:37 -07:00
configs drivers/char: remove /dev/kmem for good 2021-05-07 00:26:34 -07:00
debug printk changes for 5.13 2021-04-27 18:09:44 -07:00
dma Merge branch 'stable/for-linus-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb 2021-05-04 10:58:49 -07:00
entry A trivial cleanup of typo fixes. 2021-04-26 09:41:15 -07:00
events ARM: 2021-05-01 10:14:08 -07:00
gcov gcov: clang: drop support for clang-10 and older 2021-05-07 00:26:32 -07:00
irq gpio updates for v5.13 2021-05-05 12:39:29 -07:00
kcsan kcsan: Fix printk format string 2021-04-22 14:36:03 +02:00
livepatch Livepatching changes for 5.13 2021-04-27 18:14:38 -07:00
locking locking/qrwlock: Cleanup queued_write_lock_slowpath() 2021-05-06 15:33:49 +02:00
power PM: sleep: fix typos in comments 2021-04-08 19:37:21 +02:00
printk kernel/printk.c: Fixed mundane typos 2021-03-30 15:34:17 +02:00
rcu Merge branches 'bitmaprange.2021.03.08a', 'fixes.2021.03.15a', 'kvfree_rcu.2021.03.08a', 'mmdumpobj.2021.03.08a', 'nocb.2021.03.15a', 'poll.2021.03.24a', 'rt.2021.03.08a', 'tasks.2021.03.08a', 'torture.2021.03.08a' and 'torturescript.2021.03.22a' into HEAD 2021-03-24 17:20:18 -07:00
sched sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
time ARM: 2021-05-01 10:14:08 -07:00
trace tracing: Fix probes written to the set_ftrace_filter file 2021-05-06 10:03:38 -07:00
.gitignore .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
acct.c kernel/acct.c: use #elif instead of #end and #elif 2020-12-15 22:46:15 -08:00
async.c kernel/async.c: remove async_unregister_domain() 2021-05-07 00:26:33 -07:00
audit_fsnotify.c audit_alloc_mark(): don't open-code ERR_CAST() 2021-02-23 10:25:27 -05:00
audit_tree.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
audit_watch.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
audit.c lsm: separate security_task_getsecid() into subjective and objective variants 2021-03-22 15:23:32 -04:00
audit.h audit: avoid -Wempty-body warning 2021-03-24 12:11:48 -04:00
auditfilter.c lsm: separate security_task_getsecid() into subjective and objective variants 2021-03-22 15:23:32 -04:00
auditsc.c audit/stable-5.13 PR 20210426 2021-04-27 13:50:58 -07:00
backtracetest.c
bounds.c
capability.c capability: handle idmapped mounts 2021-01-24 14:27:16 +01:00
cfi.c add support for Clang CFI 2021-04-08 16:04:20 -07:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpumask/hotplug: Fix cpu_dying() state tracking 2021-04-21 13:55:43 +02:00
crash_core.c kdump: append uts_namespace.name offset to VMCOREINFO 2020-12-15 22:46:18 -08:00
crash_dump.c
cred.c kernel/cred.c: make init_groups static 2021-05-06 19:24:11 -07:00
delayacct.c delayacct: Add sysctl to enable at runtime 2021-05-12 11:43:25 +02:00
dma.c
exec_domain.c
exit.c do_wait: make PIDTYPE_PID case O(1) instead of O(n) 2021-05-06 19:24:13 -07:00
extable.c
fail_function.c fault-injection: handle EI_ETYPE_TRUE 2020-12-15 22:46:19 -08:00
fork.c sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
freezer.c Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" 2021-03-27 14:09:10 -06:00
futex.c futex: Make syscall entry points less convoluted 2021-05-06 20:19:04 +02:00
gen_kheaders.sh kbuild: redo fake deps at include/config/*.h 2021-04-25 05:26:10 +09:00
groups.c groups: simplify struct group_info allocation 2021-02-26 09:41:03 -08:00
hung_task.c
iomem.c
irq_work.c irq_work: record irq_work_queue() call stack 2021-04-30 11:20:42 -07:00
jump_label.c static_call: Fix static_call_update() sanity check 2021-03-19 13:16:44 +01:00
kallsyms.c kallsyms: strip ThinLTO hashes from static functions 2021-04-08 16:04:21 -07:00
kcmp.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt sched: Core-wide rq->lock 2021-05-12 11:43:27 +02:00
kcov.c
kexec_core.c kexec: dump kmessage before machine_kexec 2021-05-07 00:26:32 -07:00
kexec_elf.c
kexec_file.c kernel: kexec_file: fix error return code of kexec_calculate_store_digests() 2021-05-07 00:26:32 -07:00
kexec_internal.h kexec: move machine_kexec_post_load() to public interface 2021-02-22 12:33:26 +00:00
kexec.c
kheaders.c
kmod.c modules: add CONFIG_MODPROBE_PATH 2021-05-07 00:26:33 -07:00
kprobes.c kprobes: Fix to delay the kprobes jump optimization 2021-02-19 14:57:12 -05:00
ksysfs.c
kthread.c Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
latencytop.c
Makefile kbuild: update config_data.gz only when the content of .config is changed 2021-05-02 00:43:35 +09:00
module_signature.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
module_signing.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
module-internal.h
module.c Summary of modules changes for the 5.13 merge window: 2021-04-30 12:29:36 -07:00
notifier.c
nsproxy.c fixes-v5.11 2020-12-14 16:40:27 -08:00
padata.c
panic.c
params.c Modules updates for v5.11 2020-12-17 13:01:31 -08:00
pid_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
pid.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
profile.c kernel: Initialize cpumask before parsing 2021-04-10 13:35:54 +02:00
ptrace.c Linux 5.12-rc8 2021-04-20 10:13:58 +02:00
range.c
reboot.c Revert "PM: ACPI: reboot: Use S5 for reboot" 2021-03-18 16:58:02 +01:00
regset.c
relay.c relay: allow the use of const callback structs 2020-12-15 22:46:18 -08:00
resource_kunit.c resource: provide meaningful MODULE_LICENSE() in test suite 2020-11-25 18:52:35 +01:00
resource.c kernel/resource: fix locking in request_free_mem_region 2021-05-07 00:26:33 -07:00
rseq.c rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs() 2021-04-14 18:04:09 +02:00
scftorture.c scftorture: Add debug output for wrong-CPU warning 2021-01-04 13:53:41 -08:00
scs.c scs: switch to vmapped shadow stacks 2020-12-01 10:30:28 +00:00
seccomp.c Merge branch 'work.file' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-05-03 11:05:28 -07:00
signal.c Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
smp.c smp: Fix smp_call_function_single_async prototype 2021-05-06 15:33:49 +02:00
smpboot.c sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
smpboot.h
softirq.c RCU changes for this cycle were: 2021-04-28 12:00:13 -07:00
stackleak.c
stacktrace.c
static_call.c static_call: Fix unused variable warn w/o MODULE 2021-04-09 13:22:12 +02:00
stop_machine.c stop_machine: Add caller debug info to queue_stop_cpus_work 2021-03-23 16:01:58 +01:00
sys_ni.c Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com> 2021-05-01 18:50:44 -07:00
sys.c sched: prctl() core-scheduling interface 2021-05-12 11:43:31 +02:00
sysctl-test.c
sysctl.c delayacct: Add sysctl to enable at runtime 2021-05-12 11:43:25 +02:00
task_work.c kasan: record task_work_add() call stack 2021-04-30 11:20:42 -07:00
taskstats.c
test_kprobes.c
torture.c torture: Replace torture_init_begin string with %s 2021-03-08 14:22:28 -08:00
tracepoint.c tracepoints: Code clean up 2021-02-09 12:27:29 -05:00
tsacct.c
ucount.c fanotify: configurable limits via sysfs 2021-03-16 16:49:31 +01:00
uid16.c
uid16.h
umh.c kernel/umh.c: fix some spelling mistakes 2021-05-07 00:26:34 -07:00
up.c A set of locking related fixes and updates: 2021-05-09 13:07:03 -07:00
user_namespace.c kernel/user_namespace.c: fix typos 2021-05-07 00:26:34 -07:00
user-return-notifier.c
user.c
usermode_driver.c bpf: Fix umd memory leak in copy_process() 2021-03-19 22:23:19 +01:00
utsname_sysctl.c
utsname.c
watch_queue.c watch_queue: rectify kernel-doc for init_watch() 2021-01-26 11:16:34 +00:00
watchdog_hld.c
watchdog.c watchdog: cleanup handling of false positives 2021-04-30 11:20:36 -07:00
workqueue_internal.h
workqueue.c CFI on arm64 series for v5.13-rc1 2021-04-27 10:16:46 -07:00